Sonography plays a key role in the initial evaluation and monitoring of ventricular dilatation in the newborn. The use of supplemental imaging approaches by the mastoid fontanelle and foramen magnum can help identify the cause and location of obstruction. Duplex Doppler of intracranial vessels during anterior fontanelle compression is a useful indicator of altered cranial compliance in these infants. Additional views of the thoracolumbar spine can help identify which infants will likely benefit from lumbar puncture for therapy of progressive ventricular dilatation.